Migrate OpenSCD to Rollup

[pascalwilbrink]

With the new version of Lit (2.2.7), we can start using rollup as a bundler. Snowpack is not supported any longer. Example:

https://github.com/openscd/open-scd-core

Todo: Migrate to Rollup - Remove Snowpack - Create rollup configuration - Start using web-dev-server (dependency) - npm start should still work with the index.html

Acceptance criteria:

• No usage of Snowpack any longer
• Build output should keep the hierarchy / directory tree (tree shaking is nog possible in order to load plug-in dynamicly)

[Sander3003]

Covert it into a spike: create a POC for the things above.